Electrical thermal control apparatus and method for curing insulation on a winding

ABSTRACT

Improved electrical control apparatus is provided for curing insulation on a winding. The apparatus comprises means for automatically energizing and deenergizing a winding to maintain the temperature of the winding within a predetermined temperature range in order to cure a heat curable resinous insulating composition on the winding.

United States Patent n 1 3,560,713

[72] Inventor Junior Harold Troy [56] ReferencesCited Monroev llm PB- UNITED STATES PATENTS 1 1 pp 681462 3.044.968 7/1962 Ichikawa 338/22 1 Filed Dec-11.196 3.062.941 11/1962 White 219/505 1 Patented 1971 3.088.058 4/1963 Jakel 335 277 [73] Assignee Westinghouse Electric Corporation I Pittsburgh, p Primary bxam1ner-Bernard A. Gilheany a corporation of Pennsylvania [54] ELECTRICAL THERMAL CONTROL APPARATUS AND METHOD FOR CURING INSULATION ON A Assistant Examiner-F. E. Bell Attorneys-A. T. Stratton, C. L. Mcl-Iale and W. A. Elchik ABSTRACT: Improved electrical control apparatus is provided for curing insulation on a winding. The apparatus comprises means for automatically energizing and deenergizing a winding to maintain the temperature of the winding within a predetermined temperature range in order to cure a heat curable resinous insulating composition ,on the winding.

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WITNESSES INVENTOR JUNIOR HAROLD TROY ATTORNEY I I ELECTRICAL THERMAL CONTROL APPARATUS AND METHOD FOR CURING INSULATION ON A WINDING BACKGROUND OF THE INVENTION It is generally old in the art to cure insulation on an electrical winding by passing current through the winding in order to provide heat for curing the insulation. The success of this process has been limited because of a lack of an efficient, simple, economical and effective temperature control. Heretofore, expensive and complicated optical pyrometer systems and controls, thermocouple systems, resistance temperature detector schemes, and typical thermostat control systems have been tried with varying degrees of success. The optical pyrometer method has been reasonably successful. This method, however, is expensive initially and required good maintenance.

Thus, an object of this invention is to provide an improved economical electrical thermal control apparatus for curing insulation on a winding.

Another object of this invention is to provide an improved process of insulating a winding.

SUMMARY OF THE INVENTION A solventless liquid epoxy resin impregnating composition is cured on a winding by means of heat generated in the winding by current flowing through a main circuit through the winding. A sensor, having a first predetermined resistance value at a first predetermined temperature and a second predetermined resistance value higher than the first predetermined resistance value at a second predetermined temperature higher than the first predetermined temperature, is embedded in the winding and coupled to a solid state resistance responsive relay which is in turn coupled, through an interposing relay, to the main relay that controls the main circuit. The sensor, solid state relay, interposing relay and operating coil of the main relay are coupled in a controlling circuit that is connected to a power source and that is controlled by means of a switch. The contacts of the relay are connected to control the main circuit which is energized through another power source. The sensor, although coupled in the controlling circuit, is freely positionable. When it is desired to treat a winding, the winding is placed in a holder and the sensor is embedded in the winding. A solventless liquid epoxy resin impregnating composition is then applied to the winding. The switch of the controlling circuit is then closed to energize the solid state relay to thereby operate the interposing relay to thereby operate the main relay to a closed position whereupon the current in the main circuit generates heat in the winding. When the temperature of the winding reaches the second predetermined temperature value, the solid state relay responds to the second predetermined resistance value of the sensor to operate the interposing relay to thereby operate the main relay to open the main circuit. With the main circuit open the temperature of the winding drops, and when the temperature reaches the first predetermined temperature value the solid state relay responds to the first predetermined resistance value of the sensor to operate the interposing relay to thereby operate the main relay to close the main circuit again energizing the winding to heat the winding. The winding temperature is thus automatically maintained within the desired temperature range during the curing process. Signal lights are provided in order to provide a visual indication of whether the main circuit is energized or deenergized. When the insulation has properly cured, the switch is operated to turn the controlling circuit off and the main power source is turned off. The leads are disconnected from the winding, and the sensor leads are clipped ofi close to the winding. Thereafter, the insulating winding is removed from the holder and allowed to cool. Excellent results have been obtained by applying to windings a .003 inch to .006 inch build of diglycidyl ether of bisphenoI-A having an epoxy equivalent weight from 175 to 195 and a viscosity of about 5000 to 10,000 centipoises at 25 C. catalyzed with 3 phr. of 2-ethyl-4-methy1imidazole, and by maintaining a temperature of C. to C. at the windings for a period of from 15 to 30 minutes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a top plan view, with parts broken away, of electrical control apparatus constructed in accordance with principles of this invention;

FIG. 2 is a side view, with parts broken away and with parts shown in section of the apparatus of FIG. 1; and

FIG. 3 is a view of a mounting means for the winding with the winding and holder being shown in perspective and with the circuit of the apparatus of FIGS. 1 and 2 being shown schematically.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is shown therein electrical thermal control apparatus 5 for providing controlled tempera ture to cure insulation 7 on a winding 9. The winding 9 is supported on a holder I3 that is supported on a plate 17. A gear 19 is operated by a worm gear 21 to turn the plate 17 and holder 13 over to reverse the position of the winding. The gear 21 is operated by a handle 23. The holder for the coil 9 is supported on a base 25.

The electrical thermal control apparatus 5 comprises a base plate 27 having a receptacle portion 29 mounted thereon. An openable cover 30 is pivotally mounted on the receptacle portion 29. A main relay or contactor 31 is supported on the plate 27 outside of the receptacle part 29. The main relay 31 comprises a main relay coil 33 for operating three bridging contact structures 35 for opening and closing three lines 37 that are connected to a three-phase power source X. The lines 37 are connected to the three-phase coil or winding 9 to energize the winding 9 when the main relay 3] is closed. The main relay 3] is a three-pole relay of the type more specifically described in the patent to J. P. Conner et al., U.S. Pat. No. 3,296,567, issued Jan. 3, 1967. The main relay 31 may be any of a number of standard types of relays or contactors available on the market.

The main relay 31 is operated by the coil 33 thereof which is connected in a controlling circuit that is connected to a singlephase power source Y. The controlling circuit comprises a pair of lines L1 and L2 that are connected to the power source Y. A double-pole single-throw switch 39, that is mounted on a sidewall of the receptacle 29 (FIGS. 1 and 2), is manually operated to open and close the controlling circuit. A solid state resistance responsive relay M is mounted within the receptacle 29 and coupled to an electromechanical relay 43 that is also supported in the receptacle 29. The resistance responsive relay 4] is an adjustable relay of the type more specifically described in the patent to F. T. Thompson, U.S. Pat. No. 3,504,196 issued Mar. 31, 1970. The interposing relay 43 is of the type more specifically described in the patent to G. Jake], U.S. Pat No. 3,088,058, issued Apr. 30, 1963. The main relay operating coil 33 is connected across the lines L1, L2 by means of a pair of bridging contact structures 45 and 47 of the interposing relay 43. The operating coil 49 of the interposing relay 43 is coupled to the resistance responsive relay 41 for operation in a manner to be hereinafter described. A pair of conductors 51 and 53 connect the lines LI and L2 respectively to the resistance responsive relay 41. A pair of conductors 55 and 57 are connected to the resistance responsive relay 41 and connected in series with a sensor 59.

The sensor 59 is a thermistor of the general type described in the patents to Yoshio Ichikawa, U.S. Pat. No. 2,976,505 issued Mar. 21, 1961, and U.S. Pat. No. 3,044,968 issued Jul. 17, 1962. The sensor has a positive coefficient of resistance with the resistance changing rapidly with temperature change within a predetermined temperature range. The sensor 59 is designed, for example, to have a resistance of 2,000 ohms or less at a temperature less than 135 C.; a resistance of 2,000 ohms at 135 C., and a resistance of 5,000 ohms at 145 C. The resistance increases from 2,000 ohms to 5,000 ohms as the temperature rises from 135 C. to 145 C., and decreases from 5,000 ohms to 2,000 ohms as the temperature falls from 145 C. to 135 C. Sensors are built in various sizes; but the ones that are preferred for use in this invention are in the order of .156 inch diameter and .250 inch in length with a small size lead wire brought out at each end. Thus, these sensors are so small that they can easily be located in the winding so that they can very closely follow the temperature cycle of the copper.

The sensor 59 is coupled to the solid state resistance responsive relay 41 by means of the lines 55, 57. The solid state resistance responsive relay 41 is of the type more specifically described in the application of F.T. Thompson, Ser. No. 646,672, filed June 16, 1967, now U.S. Pat. No. 3,504,196, and assigned to the assignee of the instant application. The solid state resistance responsive relay 41 is adjustable to operate, in response to the resistance of the sensor 59, in two modes which correspond by way of example to dropped out" and picked up" modes or states of an electromagnetic relay. The resistance responsive relay 41 is adjusted to operate in one mode thereof to energize the coil 49 when the switch 39 is closed and the temperature of the sensor 59 is room temperature so that the resistance of the sensor is at or below a first predetermined value such, for example, as 2,000 ohms; to operate continually in said one mode until the resistance of the sensor 59 reaches a second and higher predetermined value such, for example, as 5,000 ohms; to switch to the other mode thereof to deenergize the coil 49 when the resistance of the sensor reaches the second predetermined value; to remain in said other mode thereof to thereby maintain the coil 49 deenergized until the resistance in the sensor falls to said first predetermined value; and to switch to said one mode thereof to energize the coil 49 when the resistance in the sensor reaches said first predetermined value. The solid state resistance responsive relay 41 will continue to operate in the foregoing manner, so long as the switch 39 is closed, effecting energization of the coil 49 when the resistance of the sensor falls to the first predetermined value such, for example as 2,000 ohms and to effect deenergization of the coil 49 when the resistance of the sensor rises to the second predetermined value such, for example, as 5,000 ohms. After the apparatus has operated in the foregoing manner for a predetermined time, the switch 39 can be opened to thereby deenergize the controlling circuit. The interposing relay 43 is an electromechanical relay of the type described in the patent to G. Jakel, U.S. Pat. No. 3,160,730, issued Dec. 8, 1964.

OPERATION A winding 9 is inserted into the holder 13 and connected through the main relay 31 is a three-phase power source X. The desirable power requirement is three times the nameplate (N.P.) current rating of the winding 9. The sensor 59 is then embedded in the winding 9. The switch 39 is then closed to energize the controlling circuit. With the switch 39 closed, the resistance responsive relay 41 operates to energize the coil 49 of the interposing relay 43 whereupon the bridging contacts 45, 47 are moved to the closed position to energize the coil 33 of the main relay 31 and whereupon a bridging contact member 65 is operated to an open position. An indicating lamp 67, which may be a red lamp, is energized through the contact 47 to indicate that the main relay 31 is in the closed position energizing the winding 9. When the relay coil 33 is energized the contacts 35 of the main relay 31 are closed and the winding 9 is energized from the power source X.

When the winding 9 is energized, an epoxy resin is applied to the winding. The epoxy resin, which is a solventless liquid epoxy resin impregnating composition having an initial low viscosity, is applied to the winding 9 with a brush or other suitable dispenser. The heat generated by the current in the winding 9, causing the liquid epoxy resin to thin down to a lower viscosity, and the 60 cycle vibration of the energized winding 9 contribute to obtaining a good permeation of the epoxy resin through the winding 9. In general, only a .003 to .006 inch build of epoxy resin is required on the winding. After the resin has been applied to the one side of the winding 9, the handle 23 is operated to operate through the gears 21. 19 toturn the holder 17 and winding 9 over, and the resin is similarly applied to the other side of the winding 9. After the resin has been applied to the complete winding, the apparatus is permitted to operate for a desired length of time such, for example, as from 15 to 30 minutes. During this time, the apparatus automatically operates to maintain the temperature of the winding within the desired range such, for example, as from C. to C.

When the switch 39 is first closed, the resistance value of the sensor 59 is below the low or first predetermined resistance value since the sensor is at room temperature. Thus, the solid state resistance sensing relay 4], in the first mode thereof, operates to energize the interposing relay coil 49 to thereby energize the main relay coil 33 to thereby energize the winding 9. The winding 9 remains energized until the temperature of the sensor reaches the high or second predetermined temperature value. When the temperature of the sensor reaches the second predetermined temperature value, the resistance of the sensor reaches the high or second predetermined resistance value, and the solid state resistance responsive relay 4!, which is adjusted or pretuned to switch to the second mode of the two modes thereof in response to the second predetermined resistance value of the sensor, switches to the second mode thereof to deenergize the coil 49 whereu pon the contacts 45, 47 are automatically opened to deenergize the main relay coil 33 whereupon the contacts 35 are automatically opened to open the circuit through the winding 9. When the coil 49 is deenergized, the bridging contact 65 is automatically moved to the closed position to energize an indicating lamp 69, which may be a green indicating lamp, to indicate that there is no current passing through the winding 9. With the winding 9 deenergized, the temperature of the winding will fall slowly until the temperature reaches the first predetermined temperature value. When the temperature in the sensor reaches the first predetermined temperature value, the resistance of the sensor 59 reaches the first predetermined resistance value, and the solid state resistance responsive relay 4!, which has been adjusted or pretuned to switch to the first mode of the two modes thereof when the resistance of the sensor 59 reaches the first predetermined resistance value, switches to the first mode thereof to energize the coil 49 of the interposing relay 43 whereupon the contacts 47, 45 are automatically closed to energize the coil 33 of the main relay 31 to thereby close the main relay 31 to energize the winding 9. When the coil 49 of the interposing relay 43 is energized the bridging contact 65 is operated to the open position deenergizing the lamp 69, and the bridging contact 47 is operated to the closed position again energizing the lamp 67. With the controlling circuit automatically operating to energize the main relay coil 33 when the temperature of the sensor 59 falls to the first predetermined temperature value and to automatically deenergize the main relay coil 33 when the temperature of the sensor 59 reaches the second predetennined temperature value, the temperature is maintained within the desired predetermined temperature range as long as the switch 39 is in the closed position. When the desired curing time has elapsed, the switch 39 is opened deenergizing the controlling circuit and opening the main relay 31. The leads of the sensor 59 are then clipped off close to the winding without damaging the treated winding, and the winding is removed from the holder and permitted to cool whereupon thewinding is ready for use in the desired application. The sensor 59, which is relatively inexpensive, need not be salvaged.

EXAMPLE A winding having a nameplate (N.P.) current rating of 25 amps at 440 volts was placed a holder and connected through a main contactor 31 to a three-phase 440 volt alternating current power source adjusted to deliver a current of 75 amps. The controlling circuit was connected to a 110 volt alternating current single-phase power source for controlling the coil 33 of the main relay 31. The sensor 59 was embedded in the winding. The sensor was designed to have a resistance of 2,000 ohms or less at temperatures less than 135 C.: a resistance of 2.000 ohms at 135 C.: and a resistance of5,000 ohms at 145 C. The sensor was designed so that the resistance would increase from 2,000 ohms to 5.000 ohms as the temperature rose from 135 C to 145 C and decrease from 5.000 ohms to 2,000 phms as the temperature dropped from 145 C. to 135 C. The resistance responsive relay 41 was adjusted to operate in one mode thereof to energize the coil 49 when the switch 39 was closed and the temperature of the sensor 59 was at room temperature so that the resistance of the sensor was at or below 2,000 ohms: to operate continually in said one mode maintaining the coil 49 energized until the resistance of the sensor 59 reached 5,000 ohms; to switch to the other mode thereof to deenergize the coil 49 when the resistance of the sensor reached 5,000 ohms: to remain in said other mode thereby maintaining the coil 49 deenergized until the resistance in the sensor dropped to 2,000 ohms; to switch to said on mode thereof to energize the coil 49 when the resistance in the sensor reached 2,000 ohms; and to continue energizing and deenergizing the coil 49 in response to the resistance of the sensor 59 in the foregoing manner so long as the switch 39 was closed. With the resistance responsive relay 41 properly adjusted, the switch 39 was closed and since the temperature of the sensor 59 was at room temperature below 135 C., so that the resistance of the sensor 59 was at or below 2,000 ohms, the resistance responsive relay 41 operated in the one mode thereof to energize the coil 49 of the relay 43 closing the contacts 45, 47, to thereby energize the coil 33 of the main relay 31 to close the contacts 35 to energize the winding 9. A solventless liquid epoxy resin impregnating composition was then applied, with a brush, to the top side of the winding 9 until the slot section was fully permeated and a thickness of from .003 to .006 of an inch was obtained on the end winding. The specific composition was diglycidyl ether of bisphenol-A having an epoxy equivalent Weight from about 175 to 195 and a viscosity of about 5,000 to 10,000 centipoises at C. catalyzed with 3 phr of 2-ethyl-4-methylimidazole. The composition had an initial low viscosity which in conjunction with the processing temperature and 60 cycle vibration of the winding contributed to obtaining an excellent permeation of the winding. After the composition was applied to the one side of the winding, the holder was turned over and the composition was similarly applied to the other side of the winding. The current flowing through the winding 9 brought the temperature of the winding 9 and the sensor 59 up to the 135 C. 145 C. rangewithin approximately 2 minutes. When the temperature of the winding 9 and sensor 59 reaches 145 C., the resistance of the sensor 59 reached 5,000 ohms whereupon the resistance responsive relay 4] switched from the one mode thereof to the other mode thereof to deenergize the coil 49 dropping out the relay 43 to thereby drop out the relay 31 deenergizing the winding 9. The resistance responsive relay 41 remained in said other mode to maintain the winding 9 deenergized until the temperature of the winding 9 and sensor 59 dropped to 135 C. When the temperature of the winding 9 and sensor 59 reached 135 C.. the resistance responsive relay 41 switched from said other mode thereof to said one mode thereof to energize the coil 49 picking up the relay 43 to thereby energize the coil 33 picking up the relay 31 to energize the winding 9. The resistance responsive relay 41 operated in said one mode thereof to maintain the winding 9 energized until the temperature of the winding 9 and sensor 59 reached 145 C. whereupon the resistance responsive relay 41 switched to said other mode thereof to deenergize the coil 49 to drop out the relay 43 to thereby deenergize the coil 33 to drop out the relay 31 to thereby deenergize the winding 9. The apparatus operated in the foregoing manner to maintain the temperature of the Winding 9 and sensor 59 within the C C. range until the switch 39 opened. During the curing time, the red lamp 67 was automatically energized while current was flowing through the winding 9 and automatically deenergized while current was not flowing through the winding 9, and the green lamp 69 was automatically deenergized while current was flowing through the winding 9 and automatically energized while current was not flowing through the winding 9 to thereby provide a visual indication of the energized or deenergized condition of the winding 9. The switch 39 was opened after a 30 minute time period to deenergize the controlling circuit dropping out the relay 43 and the relay 31 to deenergize the winding 9. The leads of the sensor 59 were then clopped off close to the insulation and the sensor 59 remained embedded in the insulated winding. The winding 9 was then removed from the holder and permitted to cool whereupon the winding was ready for use in the desired application. A number of windings, in the order of 1,000, were similarly insulated with excellent results.

I claim: 1.[Electrical] In combination, a winding, a holder supporting said winding, electrical control apparatus for curing insulation on [a] said Winding, said apparatus comprising a main relay having a main relay operating coil, means [for] connecting said main relay to control a maincircuit through said winding, a sensor having a first predetermined resistance value at a first predetermined temperature and a second predetermined resistance value [higher than said first predetermined resistance value] at a second predetermined temperature higher than said first predetermined temperature, a resistance responsive relay means coupling said main relay operating coil said resistance responsive relay and said sensor, said sensor being [positionable whereby said sensor can be placed] positioned in proximity to said winding to respond to the heat generated in said winding by current in said maincircuit, means [for] connecting said main relay operating coil said resistance responsive relay and said sensor in a controlling circuit, said resistance responsive relay being operable in response to the resistance of said sensor to effect operation of said main relay, said apparatus being constructed and arranged such that:

with said controlling circuit being energized when the temperature in said sensor is below said second predetermined value [such that the resistance in said sensor is below said second predetermined resistance value] said resistance responsive relay operates in one mode thereof to effect energization of said main relay operating coil to thereby close said main relay to energize said winding whereupon the current generated in said winding operates to heat said winding and said sensor;

when the temperature is said sensor reaches said second predetermined value such that the resistance in said sensor reaches said second predetermined resistance value said resistance responsive relay operates in another mode thereof to effect deenergization of said main relay operating coil to deenergize said winding;

and when the temperature is said sensor falls to said first predetermined temperature value such that the resistance in said sensor [falls to] reaches said first predetermined resistance value said resistance responsive relay operates in said one mode thereof to effect energization of said main relay operating coil to thereby close said main relay to energize said winding whereby the temperature of said winding and said sensor is automatically maintained in a temperature range between substantially said first predetermined temperature value and substantially said second predetermined temperature value and substantially said second predetermined temperature value whereby a heat curable resinous insulating composition can be applied on said winding and cured for a predetermined period of time by the heat in said temperature range. 2. Electrical control apparatus according to claim 1, said sensor being positioned with at least a portion thereof embedded in said winding, and switch means manually oper- 5. Electrical control apparatus according to claim 3. said first predetermined resistance value being 2,000 ohms, said first predetermined temperature value being C.. said second predetermined resistance value being 5.000 ohms and said second predetermined temperature value being C.

64 Electrical control apparatus according to claim 5, and lamp means connected in said controlling circuit to provide a visual indication of the energized and deenergized condition of said winding. 

1. In combination, a winding, a holder supporting said winding, electrical control apparatus for curing insulation on said winding, said apparatus comprising a main relay having a main relay operating coil, means connecting said main relay to control a main circuIt through said winding, a sensor having a first predetermined resistance value at a first predetermined temperature and a second predetermined resistance value at a second predetermined temperature higher than said first predetermined temperature, a resistance responsive relay means coupling said main relay operating coil said resistance responsive relay and said sensor, said sensor being positioned in proximity to said winding to respond to the heat generated in said winding by current in said main circuit, means connecting said main relay operating coil said resistance responsive relay and said sensor in a controlling circuit, said resistance responsive relay being operable in response to the resistance of said sensor to effect operation of said main relay, said apparatus being constructed and arranged such that: with said controlling circuit being energized when the temperature in said sensor is below said second predetermined value and said resistance responsive relay operates in one mode thereof to effect energization of said main relay operating coil thereby close said main relay to energize said winding whereupon the current generated in said winding operates to heat said winding and said sensor; when the temperature in said sensor reaches said second predetermined value such that the resistance in said sensor reaches said second predetermined resistance value said resistance responsive relay operates in another mode thereof to effect deenergization of said main relay operating coil to deenergize said winding; and when the temperature in said sensor falls to said first predetermined temperature value such that the resistance in said sensor reaches said first predetermined resistance value said resistance responsive relay operates in said one mode thereof to effect energization of said main relay operating coil to thereby close said main relay to energize said winding whereby the temperature of said winding and said sensor is automatically maintained in a temperature range between substantially said first predetermined temperature value and substantially said second predetermined temperature value whereby a heat curable resinous insulating composition can be applied on said winding and cured for a predetermined period of time by the heat in said temperature range.
 2. Electrical control apparatus according to claim 1, said sensor being positioned with at least a portion thereof embedded in said winding, and switch means manually operable to open and close said controlling circuit.
 3. Electrical control apparatus according to claim 2, and an interposing relay in said controlling circuit coupled to respond to said modes of said resistance responsive relay to thereby effect energization and deenergization of said main relay operating coil.
 4. Electrical control apparatus according to claim 3, and lamp means in said controlling circuit operable to provide a visual indication of the energized and deenergized condition of said winding.
 5. Electrical control apparatus according to claim 3, said first predetermined resistance value being 2,000 ohms, said first predetermined temperature value being 135* C., said second predetermined resistance value being 5,000 ohms and said second predetermined temperature value being 145* C.
 6. Electrical control apparatus according to claim 5, and lamp means connected in said controlling circuit to provide a visual indication of the energized and deenergized condition of said winding. 